I think it's a chemical imbalance. That's been my experience; I'm sure others have different views. Because it's chemical, in my view, I find diet plays a very significant role in feeling tone.

I've always wondered why it is necessary to prescribe such high dosages of Lithium, for example, when the brain can use only a very tiny level for functioning. Something else is happening for the brain to require that much. Same is true of other meds. I think things are interfering with the metabolism which is more related to gastric circumstances than anything, IMHO. I have lived long enough to experiment and found diet a strong factor in this illness.

Just for kicks, the highest number (about 95%)of neurotransmitters are in the digestive system, not the brain. I've read that knowledge of that may lead psychiatry to take a different stance on the treatment and medications of bipolar illness.